Modeling Scenarios
with Sequence Diagrams
Mustafa K. Isik
April 23rd, 2007

Scenario - Definition
• sequence of processing steps
• to be executed under certain circumstances
• defined goal
• begins with a triggering event
• ends by completing task successfully or
failing

Scenario - Definition (2)
• can document business processes (n : 1)
• visualization of a specific execution instance of the
respective business process
• two fundamental description categories
• successful execution of a process
• failed execution of a process

UML - Visualization of
dynamic activities
• Object Diagram
• system snapshot on object level, not suitable for
modeling scenarios
• Communication Diagram (formerly known as
Collaboration Diagram)
• models object collaboration during operation
execution
• Sequence Diagram
• precise depiction of chronological execution order

Sequence Diagram
• precise description of activities
• permits for discussion of technical correctness
• suitable as means for design and
implementation communication
• emphasizes chronological aspect of dynamic
behavior

Sequence Diagram -
Components
Object
objName : ClassName
life line
X
end of life

Sequence Diagram -
Components (2)
objA : ClassName objB : ClassName
message(parameter)
activation
bar (optional)

Sequence Diagram -
Messages / Actions
synchronous
asynchronous
Return (opt.)
<<create>> obj : Class
Instantiation
<<destroy>>
Dereferencing X

Example
order : OrderControl chk : CardChecker
checkCredit()
<<create>>
card : CreditCard
charge(card)
<<destroy>>
X

Literature
• Balzert, H 2000, Lehrbuch der
Softwaretechnik - Software-Entwicklung, 2.
Aufl., Spektrum Akad. Verlag, Heidelberg,
Chapter 2.9.5
• Pilone, D 2004, UML Kurz & Gut, O’Reilly, S.
64 - 68
• Hamilton, K, Russell, M, 2006, Learning UML
2.0, O’Reilly, Chapter 7